Humidity conditioning air system for pneumatically driven device

ABSTRACT

An air system in which the supply air from a compressed air source is supplied to a pneumatically driven device through a pneumatic line, including humidity conditioning tubes used for the whole or a part of the pneumatic line. This humidity conditioning tube includes a polymer material having moisture selective permeability in both inward and outward directions according to steam partial pressure in and outside thereof, and the supply air supplied to the pneumatically driven device through the tube is dehumidified or humidified by this humidity conditioning tube. An air system can suppress generation of mist or the like in supply air without shortening a life of a device caused by supply of low dew-point air to the pneumatically driven device.

TECHNICAL FIELD

The present invention relates to a humidity conditioning air system forpneumatically driven device that conditions humidity in supply air froma compressed air source through a pneumatic line and then supplies theair to the pneumatically driven device.

BACKGROUND ART

In air systems in which a pneumatically driven device such as an aircylinder is driven by supply air from a compressed air source, when thesupply air from the compressed air source is supplied toward thepneumatically driven device through a switching valve or when beingdischarged from the pneumatically driven device, the air isadiabatically expanded inside piping or the pneumatically driven device,and the temperature is lowered and moisture in the air is condensed toform a mist in many cases. This mist gradually grows and is condensedwhile supply and discharge of the air is repeated, which causes rusts inthe pneumatically driven device or deteriorates a lubricant and disturbssmooth operation of the pneumatically driven device.

In order to prevent the condensation, such an art has been widely knownthat a dehumidifier device made of a large number of fiber polymerpermeation membranes having selective moisture permeability called ashollow fiber membrane in general is used to dehumidify the supply airsupplied to the pneumatically driven device and to supply dry air to thepneumatically driven device. The dehumidifier device usuallyaccommodates a hollow fiber membrane module formed by arranging a largenumber of hollow fiber membranes side by side inside a housing so as toflow purge air for discharging moisture separated around the hollowfiber membrane.

Installation of such dehumidifier devices is an effective measure toprevent condensation even when the temperature is lowered by theadiabatic expansion. But since the dehumidifier device should beinstalled in a pneumatic line between the compressed air source and thepneumatically driven device, not only that a cost is required forinstallation of the dehumidifier device but an installation space forthe dehumidifier device should be also considered, which further raisesthe cost.

On the other hand, a semiconductor plant or the like has a pneumaticline through which a low dew-point air (super dry air) is supplied allthe time, there are an increasing number of cases that the air is alsoflown through a pneumatic line to which a pneumatically driven device isconnected for the above condensation prevention measure.

However, including installation of the dehumidifier devices, if thefully dehumidified low dew-point air is supplied to the pneumaticallydriven device, grease used at a portion in the pneumatically drivendevice where parts are in sliding contact with each other or rotatingtends to be easily evaporated and shortens the life of the pneumaticallydriven device, which is a problem.

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

The present invention has a technical object to provide a humidityconditioning air system for pneumatically driven device which cansuppress generation of mist or condensed water in supply air whilerestricting shortening of life of the pneumatically driven device due tosupply of dehumidified low dew-point air to the pneumatically drivendevice.

More specifically, a technical object of the present invention is toprovide a humidity conditioning air system for pneumatically drivendevice configured to humidify supply air if the air to the pneumaticallydriven device is fully dehumidified or to have the moisture transpiredto the outside if a partial pressure of steam generating mist orcondensed water in the supply air becomes high.

Also, another technical object of the present invention is to provide ahumidity conditioning air system for pneumatically driven device whichenables desired humidity conditioning only by means made of a specialmaterial for a humidity conditioning tube constituting the whole or apart of a pneumatic line without disposing the above-mentioneddehumidifier device in the pneumatic line.

Means for Solving the Problems

In order to achieve the above objects, the present invention is ahumidity conditioning air system for supplying supply air from acompressed air source to a pneumatically driven device through apneumatic line in which a humidity conditioning tube is used for thewhole or a part of the pneumatic line between the compressed air sourceand the pneumatically driven device, the humidity conditioning tube ismade of a polymer material having moisture selective permeability inboth inward and outward directions according to steam partial pressurein and outside the tube, the humidity conditioning tube has a diameterwhich can be used at least as piping for a general-purpose pneumaticsystem, and the supply air supplied to the pneumatically driven devicethrough the humidity conditioning tube is dehumidified or humidified bymoisture selective permeability in both inward and outward directions inthe humidity conditioning tube.

The humidity conditioning tube can be assembled to an air feed/dischargesystem of the driven device, which is an end on the pneumatically drivendevice side of the pneumatic line between the compressed air source andthe pneumatically driven device or specifically, at an airfeed/discharge port or a pipe joint or the like connected thereto.

In the humidity conditioning air system for pneumatically driven deviceaccording to the present invention, the humidity conditioning tube maybe arranged in plural in the pneumatic line according to a volume of thepneumatically driven device.

Also, in a preferred embodiment of the humidity conditioning air systemfor pneumatically driven device according to the present invention, ifthe supply air from the compressed air source is a low dew-point air,the system is configured to humidify the supply air by placing thehumidity conditioning tube made of a polymer material with moistureselective permeability in the atmosphere or humidified atmosphere andmoreover, if the supply air from the compressed air source is highdew-point air or medium dew-point air, the humidity tube made of apolymer material with moisture selective permeability is connected to aportion of the pneumatic line on the pneumatically driven device sideand placed in the atmosphere or dehumidified atmosphere to be used fordehumidification of the supply air.

In the humidity conditioning air system for pneumatically driven deviceaccording to the present invention, the humidity conditioning tube mightbe used in a mode only for the humidifying or dehumidifying of thesupply air as mentioned above, but the tube basically functions bytransferring the moisture from a portion with higher partial pressure toa portion with lower partial pressure according to steam partialpressure in and outside the humidity conditioning tube so thatcontainment of excessive moisture in the supply air introduced into thepneumatically driven device or supply of excessively dry air to thepneumatically driven device is automatically suppressed.

ADVANTAGES OF THE INVENTION

According to the humidity conditioning air system for pneumaticallydriven device of the present invention mentioned above, while shorteningof a life of the pneumatically driven device caused by supply ofdehumidified low dew-point air to the pneumatically driven device isrestricted, generation of mist or condensed water in the supply air canbe suppressed and more specifically, if the supply air to thepneumatically driven device is fully dehumidified, it can be humidified,while if the steam partial pressure generating mist or condensed waterin the supply air is raised, the moisture can be transpired to theoutside.

Moreover, according to the present invention, desired humidityconditioning can be executed only by means obtained by making thehumidity conditioning tube constituting the whole or a part of thepneumatic line by a special material without disposing theabove-mentioned conventional dehumidifier device in the pneumatic line.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of a humidity conditioning airsystem for pneumatically driven device according to the presentinvention and shows a dehumidification mode of supply air in a pneumaticline.

FIG. 2 is a schematic block diagram as above and shows a humidificationmode of the supply air in the pneumatic line.

FIG. 3 is a sectional view illustrating a mode in which the humidityconditioning air system for pneumatically driven device according to thepresent invention is configured by assembling a humidity conditioningtube to the pneumatically driven device.

FIG. 4 is a sectional view illustrating a mode in which the humidityconditioning tube is assembled to a pipe joint mounted for airfeed/discharge at the pneumatically driven device.

REFERENCE NUMERALS

-   -   1 compressed air source    -   2 pneumatic line    -   3 pneumatically driven device    -   10, 10 a, 10 b humidity conditioning tube

BEST MODE FOR CARRYING OUT THE INVENTION

FIGS. 1 and 2 show an outline of an embodiment of a humidityconditioning air system for pneumatically driven device according to thepresent invention.

The humidity conditioning air system for pneumatically driven devicebasically is configured such that supply air from a compressed airsource 1 is supplied to a pneumatically driven device 3 through apneumatic line 2 so as to drive the pneumatically driven device 3 bythis supply air, and an electromagnetically driven 5-port switchingvalve 4 for controlling drive of the pneumatically driven device 3 inregular use is interposed in the pneumatic line 2.

In the figures, an air cylinder is shown as the typical pneumatic drivendevice 3, and this air cylinder has a piston 6 sliding inside a cylindertube 5 and a rod 7 extending from the piston 6, and on both sides of thepiston 6, a head-side pressure chamber 8 a having a port 9 a and arod-side pressure chamber 8 b having a port 9 b are formed,respectively. By switching of the switching valve 4, the supply air fromthe compressed air source 1 is introduced into the one pressure chamber,while the supply air having been introduced into the other pressurechamber is discharged, and this operation is repeated alternately to theboth pressure chambers so that the piston 6 goes back and forth.

The air cylinder shown here is merely an example of the pneumaticallydriven device, and application of the humidity conditioning air systemof the present invention is not limited to the air cylinder. Also, it isonly necessary that the 5-port switching valve 4 controls drive of thepneumatically driven device 3 and it is not limited to the illustratedexample.

At a part of the pneumatic line 2 between the compressed air source 1and the pneumatically driven device 3, humidity conditioning tubes 10 a,10 b made of a polymer material with moisture selective permeability areconnected. The humidity conditioning tube is made of a polymer materialsuch as fluorine resin polymer used as a material for a hollow fibermembrane or the like and having moisture selective permeability throughwhich air does not permeate but moisture in the air permeates both ininward and outward directions according to steam partial pressure in andoutside the tube.

The humidity conditioning tubes 10 a, 10 b are connected to a partbetween the one output port 4 a of the switching valve 4 and the oneport 9 a of the air cylinder constituting the pneumatically drivendevice 3 as well as a part between the other output port 4 b of theswitching valve 4 and the other port 9 b of the air cylinder,respectively, that is, a part of a flow passage connected to each portin the pneumatically driven device 3 in the pneumatic line 2,respectively.

The humidity conditioning tube can be connected to the whole of thepneumatic line 2 or more specifically, between the one output port 4 aof the switching valve 4 and the one port 9 a of the air cylinder aswell as between the other output port 4 b of the switching valve 4 andthe other port 9 b of the air cylinder and moreover between thecompressed air source 1 and an input port 4 p of the switching valve 4but may be used in a part of the pneumatic line 2 in the aboveconnection mode or another connection mode.

The humidity conditioning tubes 10 a, 10 b in the humidity conditioningair system are basically used instead of a piping tube connecting thegeneral pneumatically driven device to the compressed air source andthus, it needs to have a feeding function of compressed air similar tothe piping tube. More specifically, the humidity conditioning tube has adiameter for piping such that the supply air which can flow through atleast one of them can drive a small-sized general-use pneumaticallydriven device, and it is desirable that instead of a large number ofsmall-diameter pieces used at the expense of a flow rate in order toimprove the moisture selective permeability as a whole, an innerdiameter and length are provided with which a pressure loss of thesupply air flowing between the both ends can be ignored.

For example, in the JIS standards, the minimum diameter of polyurethanefor piping in a pneumatic system is specified as [outer diameter×innerdiameter]=2×1.2 mm for the one with nominal diameter 2 and the maximumdiameter as [outer diameter×inner diameter]=12×8 mm for the one withnominal diameter 12, and this specification is desirably referred towhen determining the diameter of the humidity conditioning tube.

In manufacture of the humidity conditioning tube, it is not necessarilyadvisable to produce a large number of pieces with nominal diameter andin that case, a plurality of humidity conditioning tubes can be arrangedside by side in the pneumatic line 2 according to the volume of theconnected pneumatically driven device 3, by which manufacture of a largenumber of humidity conditioning tubes with nominal diameter can beavoided.

In the humidity conditioning air system for pneumatically driven devicehaving the above configuration, if the partial pressure of steam is highto such an extent that mist or condensed water is generated in thesupply air supplied to the pneumatically driven device 3 or in the airdischarged from the pneumatically driven device 3, or more specifically,if the supply air is non-dehumidified high dew-point air or a mediumdew-point air not having reached the low dew-point yet though it isdehumidified, the air is emitted to the outside by permeation of themoisture and naturally evaporated by which the air is dehumidified inthe humidity conditioning tube 10 a or 10 b in the pneumatic line 2 asshown in FIG. 1. The medium dew-point air refers to the air with apossibility of generation of mist or condensed air if the temperature islowered due to adiabatic expansion at discharge or the like even thoughafter some dehumidification. If the supply air to the pneumaticallydriven device 3 is low dew-point air which has been fully dehumidifiedby freezing-type air drier or the like, the steam partial pressureoutside the humidity conditioning tube is high, and as shown in FIG. 2,the supply air is humidified.

The dehumidification and humidification can be carried out only by meansobtained by making the humidity conditioning tube constituting the wholeor a part of the pneumatic line 2 of a special material, anddehumidification or humidification is automatically executed by adifference in steam partial pressures without particular operation fromoutside. Also, there is no need to dispose a dehumidifier device in thepneumatic line as in the related art.

In the humidity conditioning air system for pneumatically driven device,while shortening of a life of the pneumatically driven device 3 causedby supply of dehumidified low dew-point air to the pneumatically drivendevice 3 is suppressed, generation of mist or condensed water in thesupply air can be restricted as mentioned above.

In the humidity conditioning air system for pneumatically driven device,if the supply air from the compressed air source 1 is dehumidified lowdew-point air, by placing the humidity conditioning tubes 10 a, 10 b inthe atmosphere as shown in FIG. 2, the steam partial pressure of theoutside atmosphere of the humidity conditioning tubes 10 a, 10 b becomeshigher than the steam partial pressure in the supply air, and towhichever port of the ports 9 a, 9 b of the air cylinder the supply airis introduced, the supply air is humidified in the humidity conditioningtubes 10 a, 10 b. If the steam partial pressure in the supply air israised to an extent that mist is generated in the humidity conditioningtubes 10 a, 10 b with adiabatic expansion caused by the humidificationor the moisture contained in the supply air from the compressed airsource 1, the steam partial pressure in the humidity conditioning tubenaturally becomes higher than the steam partial pressure in theatmosphere outside the tube, and the moisture permeates the humidityconditioning tube to the outside and is transpired.

The steam partial pressure in the atmosphere is unstable and thedifference between that and the steam partial pressure in the supply airin the humidity conditioning tubes 10 a, 10 b might be decreased, whichresults in a need to increase a humidification volume. If a relativelylarge volume of humidification is necessary when low dew-point air(super dry air) or the like supplied all the time in a semiconductorplant is used for driving of the pneumatically driven device 3, measurescan be taken such that the lengths of the humidity conditioning tubes 10a, 10 b in the pneumatic line 2 are set longer or the tubes are placedin a humidified atmosphere.

On the other hand, if the supply air from the compressed air source 1 isnon-dehumidified high dew-point air and dehumidification of the air is aprincipal purpose, it is only necessary to connect the humidityconditioning tubes 10 a, 10 b to a part on the pneumatically drivendevice 3 side in the pneumatic line 2 in many cases as shown in FIG. 1,in which the length may be several cm depending on the case, and thesupply air in the pneumatic line 2 can be dehumidified by placing thetubes in the atmosphere. When the supply air is to be dehumidified, thesteam partial pressure of the air in the humidity conditioning tubes 10a, 10 b often becomes relatively higher than that of the atmosphere, andthus, the purpose of dehumidification can be achieved only by providingthe humidity conditioning tube at a part of the pneumatic line 2 in manycases. Alternatively, in order to further improve dehumidificationeffect, the whole or a majority of the pneumatic line 2 may beconstituted by the humidity conditioning tube, or the humidityconditioning tubes may be placed in the dehumidified atmosphere.

The humidity conditioning tubes 10 a, 10 b might be used in a mode inwhich only the above-mentioned humidification or dehumidification iscarried out for the supply air but the tubes basically function so as totransfer the moisture from a portion with high steam partial pressure toa portion with low steam partial pressure according to the steam partialpressures in and outside the humidity conditioning tube so thatcontainment of excessive moisture in the supply air introduced to thepneumatically driven device or supply of excessively dry air to thepneumatically driven device is automatically suppressed. Thus, thediameter, length or connection position of the humidity conditioningtubes 10 a, 10 b in the pneumatic line 2 should be set considering thosefunctions.

The humidity conditioning tubes 10 a, 10 b may be assembled to an airfeed/discharge system in the driven device 3, which is an end portion onthe pneumatically driven device 3 side in the pneumatic line 2 betweenthe compressed air source 1 and the pneumatically driven device 3, orspecifically in and outside of the ports 9 a, 9 b for air feed/dischargeor a pipe joint connected to them or the like.

FIG. 3 shows an embodiment of the humidity conditioning air system forpneumatically driven device according to the present inventionconfigured by assembling humidity conditioning units 11A, 11B having thehumidity conditioning tubes 10 a, 10 b to the ports 9 a, 9 b in thepneumatically driven device 3, and the air cylinder as the pneumaticallydriven device 3 in this embodiment has the piston 6 sliding inside thecylinder tube 5 and the rod 7 extended from the piston 6, and thepressure chamber 8 a having the port 9 a and the pressure chamber 8 bhaving the port 9 b are formed on both sides of the piston 6,respectively. The pneumatically driven device 3 is not limited to theair cylinder.

The humidity conditioning units 11A, 11B in which the humidityconditioning tubes 10 a, 10 b constructed by a polymer material havingmoisture selective permeability are built are connected to the ports 9a, 9 b, which are ends of the pneumatic line 2 between the compressedair source 1 and the pneumatically driven device 3. The humidityconditioning units 11A, 11B connect connecting members 12 a, 13 a and 12b, 13 b at the both ends to each other by the humidity conditioningtubes 10 a, 10 b, respectively, and the periphery of the tubes 10 a, 10b are covered by protective covers 14 a, 14 b with air permeability.Both ends of the humidity conditioning tubes 10 a, 10 b and theprotective covers 14 a, 14 b are fixed in each recess groove of theconnecting members 12 a, 13 a and 12 b, 13 b by a potting agent 15.

The connecting members 13 a, 13 b on the pneumatically driven device 3side in the humidity conditioning units 11A, 11B are fixed to theoutside of each of the ports 9 a, 9 b of the pneumatically driven device3, but they may be built in the pneumatically driven device 3 as long asthe humidity conditioning tubes 10 a, 10 b are held in contact with theoutside air or managed atmosphere.

FIG. 4 shows an embodiment in which the humidity conditioning tube isassembled to a pipe joint 20 mounted on the port of the pneumaticallydriven device 3 for air feed/discharge. The pipe joint 20 is configuredby connecting a simplified joint portion 21 and a pressure control unit22, and the humidity conditioning unit 22 is connected to a port for airfeed/discharge in various types of the pneumatically driven devices 3.

The simplified joint portion 21 is a known one that when a piping tube29 constituting the pneumatic line 2 is deeply inserted into a releasebush 25 internally inserted in a main body 24 as shown in the figure,the periphery of the tube 29 is sealed by a seal member 26 and at thesame time, a locking claw 27 is locked by an outer peripheral face ofthe tube 29 so that its removal is prevented, and when the release bush25 is inserted into the main body 24, lock of the locking claw 27 by theouter peripheral face of the tube 29 is released, and the tube 29 can beeasily removed from the simplified joint portion 21.

On the other hand, the humidity conditioning unit 22 is configured suchthat the both ends of the humidity conditioning tube 10 made of apolymer material having the moisture selective permeability and theprotective cover 14 with permeability covering the periphery thereof areconnected to connecting members 31, 32, and the both ends of thehumidity conditioning tube 10 and the protective cover 14 are fixed toeach recess groove in the connecting members 31, 32 by the potting agent15. At the connecting member 31 in the humidity conditioning unit 22, aconnecting screw 31 a to be connected to the port of the pneumaticallydriven device 3 is provided, and the other connecting member 32 isconfigured capable of appropriate joint by being inserted into aconnecting cylinder portion 24 a in the main body 24 of the simplifiedjoint portion 21 in an airtight manner.

As mentioned above, the humidity conditioning tube can be assembled inor outside of the port for air feed/discharge in the pneumaticallydriven device, and at least when the humidity conditioning tube isassembled on the inner side of the port for air feed/discharge in thepneumatically driven device, the pneumatic line in this specificationshould be understood to also include the air feed/discharge system to adriving pressure chamber in the pneumatically driven device.

1. A humidity conditioning air system for pneumatically driven device inwhich supply air from a compressed air source is supplied to thepneumatically driven device through a pneumatic line, wherein: ahumidity conditioning tube is connected to the whole or a part of thepneumatic line between the compressed air source and the pneumaticallydriven device, the humidity conditioning tube being constructed by apolymer material having moisture selective permeability in both inwardand outward directions according to steam partial pressures in andoutside thereof; the humidity conditioning tube has at least a diameterthat can be used as piping for a general-use pneumatic system; and thesupply air supplied to the pneumatically driven device through thehumidity conditioning tube is dehumidified or humidified by the moistureselective permeability in both the inward and outward directions in thehumidity conditioning tube.
 2. The humidity conditioning air system forpneumatically driven device according to claim 1, wherein a plurality ofthe humidity conditioning tubes are arranged side by side in thepneumatic line according to a volume of the pneumatically driven device.3. The humidity conditioning air system for pneumatically driven deviceaccording to claim 1, wherein the supply air from the compressed airsource is low dew-point air and the humidity conditioning tube is placedin the atmosphere or humidified atmosphere.
 4. The humidity conditioningair system for pneumatically driven device according to claim 1, whereinthe supply air from the compressed air source is high dew-point air ormedium dew-point air and the humidity conditioning tube is connected toa part on the pneumatically driven device side in the pneumatic line andis placed in the atmosphere or dehumidified atmosphere.
 5. The humidityconditioning air system for pneumatically driven device according toclaim 1, wherein the humidity conditioning tube is assembled to an airfeed/discharge system in the pneumatically driven device.
 6. Thehumidity conditioning air system for pneumatically driven deviceaccording to claim 2, wherein the supply air from the compressed airsource is low dew-point air and the humidity conditioning tube is placedin the atmosphere or humidified atmosphere.
 7. The humidity conditioningair system for pneumatically driven device according to claim 2, whereinthe supply air from the compressed air source is high dew-point air ormedium dew-point air and the humidity conditioning tube is connected toa part on the pneumatically driven device side in the pneumatic line andis placed in the atmosphere or dehumidified atmosphere.